Required Number of Tokens to Determine Representative Voice Perturbation Values Acoustic perturbation analyses of prolonged vowels are used in determining phonatory stability characteristics. When a number of tokens are analyzed, the average perturbation values create a stability profile of the voice. How many tokens are needed to obtain a representative perturbation value? In this study, five perturbation measures were considered, ... Research Note
Research Note  |   December 01, 1995
Required Number of Tokens to Determine Representative Voice Perturbation Values
 
Author Affiliations & Notes
  • Ronald C. Scherer
    Wilbur James Gould Voice Research Center, The Denver Center for the Performing Arts, Denver, CO
  • Vernon J. Vail
    Wilbur James Gould Voice Research Center, The Denver Center for the Performing Arts, Denver, CO
  • Chwen Geng Guo
    Wilbur James Gould Voice Research Center, The Denver Center for the Performing Arts, Denver, CO
  • Contact author: Ronald C. Scherer, PhD, Wilbur James Gould Voice Research Center, The Denver Center for the Performing Arts, 1245 Champa Street, Denver, CO 80204.
    Contact author: Ronald C. Scherer, PhD, Wilbur James Gould Voice Research Center, The Denver Center for the Performing Arts, 1245 Champa Street, Denver, CO 80204.×
Article Information
Speech, Voice & Prosody / Speech / Research Notes
Research Note   |   December 01, 1995
Required Number of Tokens to Determine Representative Voice Perturbation Values
Journal of Speech, Language, and Hearing Research, December 1995, Vol. 38, 1260-1269. doi:10.1044/jshr.3806.1260
History: Received December 7, 1994 , Accepted April 27, 1995
 
Journal of Speech, Language, and Hearing Research, December 1995, Vol. 38, 1260-1269. doi:10.1044/jshr.3806.1260
History: Received December 7, 1994; Accepted April 27, 1995

Acoustic perturbation analyses of prolonged vowels are used in determining phonatory stability characteristics. When a number of tokens are analyzed, the average perturbation values create a stability profile of the voice. How many tokens are needed to obtain a representative perturbation value? In this study, five perturbation measures were considered, namely, jitter, shimmer, harmonics-to-noise ratio, coefficient of variation for amplitude, and coefficient of variation for frequency. Subject groups were chosen on the basis of individual average perturbation values. Results indicate that, except for the harmonics-to-noise ratio, generally, the less stable the voice, the greater is the number of tokens needed to obtain representative averages. For highly stable voices, at least six tokens are suggested; for voices with normal to high levels of instability, at least 15 tokens are recommended. Regardless of vocal stability, at least 10 tokens are suggested for the harmonics-to-noise ratio measure.

Acknowledgments
This work was supported by the National Institutes of Health grant 8R01 DC00387. Appreciation is extended to R. T. Sataloff, A. D. Meyers, and the late W. J. Gould for use of selected patient data. Thanks also are given to Laura Goodwin for statistical advice and to Christopher Linker and Paula Saraceno for assistance. Special thanks are extended to Tom Doherty, Dale Metz, Stephen McFarlane, Carol Gracco, Ben Watson, and an anonymous reviewer for their helpful suggestions.
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